Tidal propagation and damping in the unconvergent and microtidal estuary of the Magdalena River – Caribbean Sea

Abstract:

At the mouth of the Magdalena river estuary (MRE) the tidal range hardly reaches 0.60 m during spring tides. When comparing the tides with the mean significant wave height in the zone which is about 2.0 m, and with the mean freshwater discharge of 7000 m³/s of the Magdalena River (and monthly minimum of 4000 m³/s) it is easy to understand why the effect of the tides in the hydrodynamic of the MRE have been systematically neglected in the scientific literature. However, recent and more robust monitoring systems field campaigns (spatially, temporally, and technologically), have revelled notorious effect of tides in the main physical processes of the estuary. The modern monitoring systems, includes sub-hourly measurements of salinity and temperature in different locations and depths along the estuary, water level gauges along the last 50 km of the Magdalena River and weather stations. This system is complemented by recurrent measurements of currents in several locations and transects of the MRE. This inter-institutional effort has allowed a renovated approach to the physical processes taking place at this mayor estuary which is fundamental for the freshwater and sediment balance of the Caribbean Sea and for the navigation, water supply, fishing and tourism of one of the main cities of Colombia. We were able to define (or re-define) the length of the MRE according to the tidal damping, the estuarine friction according to the tidal celerity, the phase lag between levels and currents, the residual circulation and the length and variability of the saline intrusion. An overview of these aspects will be presented in this talk.